Enterobacteria Enrichment Broth Mossel, Granulated

Principle And Interpretation

The family Enterobacteriaceae consists of Salmonella, Shigella and other enteric pathogens. These organisms find entry into the food system through faecally contaminated water. Majority of these organisms may be eliminated under the stringent food processing parameters. But some of these organisms may become sub lethally injured during the changes in pH, exposure to steam or heat and other unfavourable conditions (1). Therefore the important aspect of food monitoring depends upon the identification and enumeration of these injured cells, after resuscitation. EE Broth Mossel, formulated by Mossel et al (2) is recommended as an enrichment medium for bile tolerant gram-negative bacteria in the biological examination of foods (2), animal feed stuffs (2). This medium is prepared in accordance with the harmonized method of USP/EP/BP/JP/IP (3-7). Gelatin peptone and glucose monohydrate allows the growth of most of the members of Enterobacteriaceae. Brilliant green and dehydrated bile are the inhibitory agents for gram-positive bacteria. Phosphates act as a good buffering agent and neutralizes acids produced by lactose fermenters that otherwise would adversely affect the growth of the organism. Lactose negative, anaerogenic lactose-positive or late lactose fermenting Enterobacteriaceae are often missed by the standard Coli-aerogenes test. To overcome this problem, lactose is replaced by glucose in this medium. Phosphates form the buffering system of the medium. The cells damaged while drying or low pH are resuscitated in well-aerated Soybean Casein Digest Broth (MH011) for 2 hours at 25°C prior to enrichment in EE Broth. The resuscitation procedure is recommended for dried foods (8), animal feeds (9) and semi-preserved foods (10). EE Broth is an enrichment broth and should be used in conjunction with Violet Red Bile Glucose Agar (MH581). A loopful of the enriched sample from EE Broth. is subcultured onto Violet Red Bile Glucose Agar (MH581) after an initial incubation at 30-35°C for 24 hours. Typical pink colonies from MH581 are subcultured for biochemical confirmation by oxidase and fermentation reactions (11). Decimal dilutions of the food homogenate are used if the expected counts are high or else initial suspension is used. EE Broth, Mossel (MH287).